Abstract
Abstract. Biomass burning activities can produce large quantities of smoke and result in adverse air quality conditions in regional environments. In Canada, the Environment and Climate Change Canada (ECCC) operational FireWork (v1.0) air quality forecast system incorporates near-real-time biomass burning emissions to forecast smoke plumes from fire events. The system is based on the ECCC operational Regional Air Quality Deterministic Prediction System (RAQDPS) augmented with near-real-time wildfire emissions using inputs from the Canadian Forest Service (CFS) Canadian Wildland Fire Information System (CWFIS). Recent improvements to the representation of fire behaviour and fire emissions have been incorporated into the CFS Canadian Forest Fire Emissions Prediction System (CFFEPS) v2.03. This is a bottom-up system linked to CWFIS in which hourly changes in biomass fuel consumption are parameterized with hourly forecasted meteorology at fire locations. CFFEPS has now also been connected to FireWork. In addition, a plume-rise parameterization based on fire-energy thermodynamics is used to define the smoke injection height and the distribution of emissions within a model vertical column. The new system, FireWork v2.0 (FireWork–CFFEPS), has been evaluated over North America for July–September 2017 and June–August 2018, which are both periods when western Canada experienced historical levels of fire activity with poor air quality conditions in several cities as well as other fires affecting northern Canada and Ontario. Forecast results were evaluated against hourly surface measurements for the three pollutant species used to calculate the Canadian Air Quality Health Index (AQHI), namely PM2.5, O3, and NO2, and benchmarked against the operational FireWork v1.0 system (FireWork-Ops). This comparison shows improved forecast performance and predictive skills for the FireWork–CFFEPS system. Modelled fire-plume injection heights from CFFEPS based on fire-energy thermodynamics show higher plume injection heights and larger variability. The changes in predicted fire emissions and injection height reduced the consistent over-predictions of PM2.5 and O3 seen in FireWork-Ops. On the other hand, there were minimal fire emission contributions to surface NO2, and results from FireWork–CFFEPS do not degrade NO2 forecast skill compared to the RAQDPS. Model performance statistics are slightly better for Canada than for the US, with lower errors and biases. The new system is still unable to capture the hourly variability of the observed values for PM2.5, but it captured the observed hourly variability for O3 concentration adequately. FireWork–CFFEPS also improves upon FireWork-Ops categorical scores for forecasting the occurrence of elevated air pollutant concentrations in terms of false alarm ratio (FAR) and critical success index (CSI).
Highlights
With 28 % of the world’s boreal forest (552 million ha) and 9 % of the world’s forests, Canada experiences frequent wildland fires (Natural Resources Canada, 2018)
Canadian Forest Fire Emissions Prediction System (CFFEPS) improves the current fire emissions processing used by FireWork through additional processspecific considerations, including an updated North American fuel map, closer integration with forecast meteorology for treating fire behaviour, updated emission factors, and an efficient fire injection plume height parameterization based on a fire-energy thermodynamic approach (Anderson et al, 2011)
We describe CFFEPS itself and how it is integrated with the FireWork system, and we evaluate the changes in predictive skill of surface pollutant concentration forecasts important for regional Air Quality Health Index (AQHI)
Summary
With 28 % of the world’s boreal forest (552 million ha) and 9 % of the world’s forests, Canada experiences frequent wildland fires (Natural Resources Canada, 2018). For operational numerical forecast systems such as FireWork, in which model run time is a critical consideration, the parameterization typically follows either the industrial smokestack plume-rise approach of Briggs (Briggs, 1965) or a simple assumption of uniform vertical distribution below the modelled mixing height, both of which may result in an underestimation of long-range transport, as their estimates of the plume injection height are generally located below the PBL height (Mallia et al, 2018). CFFEPS improves the current fire emissions processing used by FireWork through additional processspecific considerations, including an updated North American fuel map, closer integration with forecast meteorology for treating fire behaviour, updated emission factors, and an efficient fire injection plume height parameterization based on a fire-energy thermodynamic approach (Anderson et al, 2011).
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